1. Field of the Invention
The invention described herein relates generally to a method and apparatus for the detection of chemicals and biological agents. More specifically, it relates to a handheld electronic device and a card that can be used to collect and qualify or quantify chemicals in the environment. The invention is composed of two components, an electronic device with an optical system that can read, interpret and display a range of colors developed on a pad and a card containing said pad and incorporating liquid reagent capsules that can be activated in a controlled sequence, heated, or dried, and used to generate a pattern of colors specific to a limited range of chemicals.
2. Description of the Related Art
There is a desperate need for an improved method for detecting trace levels of certain chemicals. This is best exemplified by the recent terrorist bombings that have occurred in many countries across the globe.
Thousands of soldiers and civilians have been killed and tens of thousands wounded by what are commonly known as Improvised Explosive Devices or IED's. They range from homemade explosives formed from commercially available compounds such as peroxide and acetone that were used in the second set of London bombings in 2006; to more sophisticated devices made from virtually undetectable explosives like “Semtex” and incorporating explosive formed charges.
The latter has proved to be a particularly effective killing tool in which high explosive is place below a shaped metal disk. A mobile phone or wired detonator is embedded in the explosive, which is then detonated from a remote location. The metal disk melts by the explosion and forms a liquid projectile capable of penetrating inches of steel armor plating.
Despite the impression created by various sources in public mind, there is no way to detect these explosive devices once made and hidden by the roadside. As reported by a Department of Justice Study, the variety of high explosive used by the terrorists do not produce a vapor and cannot be detected by vapor based chemical sensors that are sometimes referred to as “sniffers” or by canine units.
Furthermore there is no way to effectively detect or block the use of the mobile phone as an effective detonator. In addition, the “Humvees” and like vehicles used for protecting soldiers, cannot carry sufficient armor plating to prevent penetration by the explosive formed charges. In short, we have no effective weapon against these devices.
The matter is further complicated by the peroxide types of explosives where the components are found in nail polish and cleaning fluid. Though these compounds are easily detected by vapor, they are ubiquitous making vapor detection useless.
In a significant but less dramatic setting we lack effective portable devices for identifying traces of many other compounds such as narcotics and biological agents. Biological agents range from those organisms that could be used for bio-terror such as Anthrax spores, to important causes of food poisoning. Several incidents have occurred recently with the contamination of spinach and peanut butter where a hand held portable detector would have permitted more rapid identification and eradication of the source.
It is argued that X-ray screening of baggage is an effective deterrent to those who would try to bomb a plane but it is equally apparent that detonation of a high explosive anywhere in the airport terminal would cause as much death and disruption as detonating the explosive on the plane.
Recent events in Glasgow, Scotland illustrated this whereby the explosive device was in a car that drove into the airport terminal and would not have been detected by existing methods. Use of a hand held portable device would permit establishing a “presence” for security personnel outside the confines of the baggage screening areas providing an improved deterrent.
For trace chemical detection there are physical methods and chemical methods. Physical methods involve the interaction of the vaporized molecule with an electronic detector. One common method referred to as Ion Mobility Spectroscopy or IMS is as follows. A sample is collected onto a swipe pad. The pad is then placed in a powerful electric field or near a radiation source and the sample molecules are broken up into ions, which are smaller electrically charged fragments. These ions are then electrically accelerated into a tube against a flow of inert gas. The gas slows the ions down and they fall onto electronic detectors. How far they progress down the tube is determined by the ion's size and charge.
If a sample of TNT is collected, ionized and passed down the tubes, its component parts will fall onto the detectors at specific locations which are stored by the machine. If an unknown compound thought to be TNT is collected and ionized, and if the gas flow rate and electrical acceleration are not altered, then the particles should fall in the same locations in similar proportions and the machine will detect it as TNT.
These machines are extremely sensitive and powerful laboratory tools. However, they do not perform as well when used a screening tool due to fluctuations in atmospheric pressure, high concentrations of benign compounds, and the overall complexity of the device. These common variables cause the device to alarm when there is no explosive present or worse yet, miss a real explosive. In addition these devices require a gas supply, are heavy, expensive, and require up to 20 minutes of calibration and warm-up time before use.
A further physical method involves the use of a selective polymer to bind the explosive as the vapor passes across a sensor. This binding induces physicals change such as how it interacts with light or a microscopic increase in weight, which is then detected electronically. These devices have also proved ineffective in real world settings because there are millions of similar molecules in the environment. Some of these molecules are present in very high concentrations, and these “like” compounds non-specifically bind to the polymer and are detected or block the detection of the real agent.
To be effective in detecting many of the explosives, the sample must first be collected onto a swipe and then vaporized to travel across the sensor. To be at all effective, the binding chemicals must be able to bind only a very limited subset of molecules in a narrow range of concentration. A large sample of real compound will overwhelm the detector and require the device to be taken out of service and cleaned before continued use.
All of the physical methods require large, less portable machines, frequent calibration, extensive training and are generally expensive; costing more than $US 30,000 per unit. Though the actual analysis may take only seconds, the warm up time and calibration and repeat calibration commonly require 30 minutes to run 10 samples.
At times, for effective detection in existing methods, samples must be diluted to the effective detection range of the device, requiring preceding knowledge of the sample or repeated testing, as well as advanced expertise in this procedure.
These devices are very prone to error if moved or exposed to varying temperatures. Most systems have electrical requirements of 120 VAC and have significant consumables such as gas canisters and replacement sensors.
Chemical methods are less varied. Essentially, for the detection of explosive compounds, these methods all use a similar group of chemicals that have been published in chemistry texts for decades. These chemicals react in a liquid medium with certain functional groups on the explosives and produce an observable color change.
Similar color chemistry methods exist for narcotics and many biological molecules. In addition, specific antibodies can be labeled with a color tag and bound to the target molecules in a liquid medium. The most common example of which is the ubiquitous urine pregnancy test.
Until the present invention, chemical methods were both hazardous to perform and technically difficult to execute. They required the application of caustic and acidic compounds and heat to the test pad to produce subtle color changes that were difficult to interpret correctly by eye. Existing embodiments of the method involve the spraying on of reagents, dropping of reagents from a dropper bottle or the crushing a glass ampoule.
In some versions, the operator must adjust the procedure based on initial results. In other embodiments, operators must time the procedure carefully and ignore specific colors even if they are the correct color but develop at the wrong time. All the existing embodiments are read by human eye and are subject to error from individual color perception, ambient lighting and temperature conditions.
By way of example, one such existing color chemistry method involves the spraying of the first reagent onto a paper swipe. If no color develops or if the color is not from a selected limited grouping, then a second reagent is sprayed. Depending on the timing and color that then may be produced, a third reagent may be added. If left, the paper swipe will develop a color change itself, which must be ignored. All these changes are dramatically affected by the accuracy of spraying and the ambient temperature.
In another embodiment, the user must add drops of solution from a bottle. A timer controls the heat reaction and a pink or orange coloration indicates a positive result for some explosives, however, gray and purple colors do not. Unfortunately these colors may be produced in the presence of common compounds such as red wine or ink, and incorrectly interpreted as a positive result. If no pink or orange color develops, the second reagent is added and the heat reapplied. Again, if particular colors develop it is a positive detection, but the presence of other colors are not. The interpretation of these colors, particularly in strong or weak lighting conditions, can completely obfuscate a positive result. Additionally, the reagents deteriorate in the bottles with exposure to air, and are extremely astringent, requiring the operator to wear personal protective equipment at all times, such as safety goggles and gloves.